The present invention relates to a vehicle headlamp arranged to vary the light distribution of a headlamp by moving a movable shade.
Vehicle headlamps are arranged to emit low or high beams by causing reflectors to reflect light from light sources forward. However, because the light distribution patterns differ between low and high beams, it is common to use a light source bulb having two light sources or two light source bulbs for the purpose of switching between low and high beams.
There exists a vehicle headlamp using a single light source for switching beams, particularly, a two-lamp type headlamp using a discharge bulb as a light source bulb.
One known method for switching beams using a single light source switches beams by moving a movable shade. The movable shade is made movable by a shade driving unit between two positions where an incident light from a light source to a reflector is shaded differently.
In the aforementioned vehicle headlamp having the shade driving unit, the movable shade is movably fitted to the reflector, and the shade driving unit is fitted to the reflector before being coupled to the movable shade. Consequently, the headlamp is not assembled efficiently nor the precision of placement of the movable shade with respect to the light source readily improved.
The problem of this kind generally arises from not only switching beams from low to high by moving the movable shade but also varying light distribution of the lamp thereby.
An object of the present invention is to provide a vehicle headlamp which is designed to vary its light distribution by moving a movable shade, and which is capable of improving not only lamp assembly efficiency but also the precision of placement of the movable shade with respect to a light source.
The present invention is intended to accomplish the object above by employing a predetermined bulb supporting base.
A vehicle headlamp according to the invention comprises a light source, a reflector for reflecting light from the light source forward, a movable shade capable of shading part of light incident on the reflector from the light source, and a shade driving unit for moving the movable shade between at least two positions where an incident light shading quantity has different values.
A light source bulb as the light source is fixedly supported by the reflector via a bulb supporting base for fixedly supporting the light source bulb, and the movable shade and the shade driving unit are fitted to the bulb supporting base.
The above xe2x80x9clight sourcexe2x80x9d is not limited to a specific kind but maybe any discharge light emitting bulb portion, for example, an incandescent bulb filament of, for example, a halogen bulb.
The xe2x80x9cmovable shadexe2x80x9d may be of any kind capable of shading part of light incident on the reflector from the light source bulb and not limited to a specific configuration.
xe2x80x9cAt least two positions where an incident light shading quantity has different valuesxe2x80x9d may be more than two positions including or not including positions where a low- or high-beam light distribution pattern may be formed when the movable shade is located at one of the above positions.
The xe2x80x9cshade driving unitxe2x80x9d is not limited to a specific driving unit but may be any one so designed as to move the movable shade between at least two positions For example, the shade driving unit may comprise a solenoid, a pulse motor or the like. Further, the xe2x80x9cmoving behaviorxe2x80x9d of the movable shade by use of the shade driving unit is not restrictive but may be pivotal, linearly reciprocal or the like.
The xe2x80x9cbulb supporting basexe2x80x9d is not limited to a special sort but may be so configured that the light source bulb is fixedly supported by the reflector while the movable shade and the shade driving unit are installed.
The vehicle headlamp according to the invention is equipped with the shade driving unit for moving the movable shade, which is capable of shading part of light incident on the reflector from the light source, between at least two positions where an incident light is shaded differently. However, as the light source bulb having the light source is fixedly supported by the reflector via the bulb supporting base, the light source bulb, the movable shade and the shade driving unit together with the bulb supporting base can be operated integrally as a unit. Thereof, the unit is prefabricated before being fitted to the reflector so as to facilitate the assembling of the lamp. Moreover, the precision of placement of the movable shade with respect to the light source can also be improved.
In the vehicle headlamp configured to vary the light distribution of the lamp by moving the movable shade according to the invention, it is possible to improve not only lamp assembly efficiency but also the precision of placement of the movable shade with respect to a light source.
Although the bulb supporting base is not limited to a special sort as mentioned above, the precision of placement of the movable shade with respect to the light source is improved further by die-casting the movable shade that has excellent dimensional precision and strength.
In the aforementioned arrangement, the fixed shade for covering the movable shade substantially in front of the movable shade makes it difficult for the movable shade and its peripheral structure to be seen from the outside. In addition, the work of assembling the lamp can be facilitated by fixedly supporting the fixed shade with the bulb supporting base.
In the aforementioned arrangement, part of the reflector may be formed separately from the remaining portion of the reflector and that part of the reflector maybe formed integrally with the bulb supporting base, so that the bulb supporting base can be fixedly supported by utilizing a wider area with respect to the remaining portion of the reflector. Thus, the precision of placement of the optical system of the lamp can be increased.